[PATCH] Yama: access current->comm directly

[Kees Cook <keescook@xxxxxxxxxxxx>]

The core ptrace access checking routine already holds the task lock,
so there is no need to use get_task_comm() which just tries to take the
lock again. Drop its use and access current->comm directly.

Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 security/yama/yama_lsm.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 83554ee..20a68ca 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -279,12 +279,10 @@ static int yama_ptrace_access_check(struct task_struct *child,
 	}
 
 	if (rc) {
-		char name[sizeof(current->comm)];
+		/* task_lock is held by the caller, so use comm directly. */
 		printk_ratelimited(KERN_NOTICE
 			"ptrace of pid %d was attempted by: %s (pid %d)\n",
-			child->pid,
-			get_task_comm(name, current),
-			current->pid);
+			child->pid, current->comm, current->pid);
 	}
 
 	return rc;
-- 
1.7.0.4


-- 
Kees Cook
Chrome OS Security
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